This paper describes how one of parapsychology's most critical thinker
s, Robert H. Thouless, devised an ingenious test of survival and left
two enciphered messages that he believed unbreakable and whose secret
keys he planned to communicate after his death as proof of his postmor
tem survival. it details attempts to obtain his keys before and after
his death and the implications of negative results. It provides a repo
rt from a cipher expert who claims to have discovered Thouless's keywo
rds and to have broken one of his messages. The paper concludes by rai
sing the question of false keys.